The supported Blender versions are 2.80 and later.

Yes, you can. The blend file containing all the nodes and resources is located under uber_compositor/data/uber_compositor_nodes.blend

You can use it as you wish, with node presets or any other asset manager, or manually append the nodes.

Yes, you can. After installing it, just locate your blender addons folder ( "C:\Users\[username]\AppData\Roaming\Blender Foundation\Blender\[blender version]\scripts\addons\" in Windows) and edit the file uber_compositor\data\uber_compositor_nodes.blend and save it.